Eggs typically undergo a great deal of processing before they are ready to be sold to the consuming public. In many circumstances, for example, eggs pass through several processing stations at which they are washed, candled, weighed, graded, and packed into packages (e.g., cartons, crates, or other commercially distributed containers). Examples of such processing stations and mechanisms for conveying eggs from station to station are described, for instance, in the following U.S. patents assigned to Diamond Automations, Inc.: U.S. Pat. Nos. 4,189,898; 4,195,736; 4,505,373; 4,519,494; 4,519,505; 4,569,444; 4,750,316; 5,321,491; and 6,056,341, the entire contents of each of which are incorporated herein by reference. It is not uncommon for a facility in which these stations operate to output about one million eggs in a single day. Accordingly, to be commercially acceptable, the throughput of the stations needs to be quite high, with some stations typically processing on the order of 20,000 eggs per hour.
Because eggs are a perishable item susceptible to spoilage, egg packages typically (and often by law or regulation) have expiration dates marked on them. Many consumers, however, move eggs from their packages into special receptacles in their refrigerators. When this is done, the consumer is no longer able to evaluate the expiration date of individual eggs prior to using them.
Furthermore, certain governmental bodies, e.g., the United States Food and Drug Administration (FDA), the United States Department of Agriculture (USDA), and various state governments, currently do not allow retailers to “repack” eggs, i.e., to move eggs from one package to another. This restriction can result in tremendous waste because whenever the integrity of even a single egg in a package in the hands of a retailer is compromised (e.g., is broken), the entire package of eggs must be discarded.
Several techniques for marking individual eggs with expiration dates and the like have been proposed. One such approach is to use vegetable dyes or other water-soluble ink products to mark eggs. Such products, however, have a tendency to leak into the interior of eggs and can result in undesirable ink spots within them. The tendency of such products to wash off or fade also means that such marking are susceptible to tampering and even unintentional loss of integrity (e.g., dripping and smearing from condensation and handling), and has generally limited their acceptance.
It is also known to use lasers to mark indicia onto perishable products for the purpose of tracking their pedigree and/or integrity (e.g., using date codes and/or traceability codes), as well as for allowing textual or graphical advertising messages to be disseminated via such products. An example of a system for laser marking such information on hen eggs is described, for example, in U.S. Patent Application Publication No. 2008/0223834 (“the '834 Application”), published on Sep. 18, 2008. The disclosure of the '834 Application is incorporated herein by reference in its entirety.
The approach described in the '834 Application is to laser mark information on eggs as they are conveyed at high speed during the grading process. Although this approach has proven effective for certain applications, the extremely high throughput of the grading machines, the lack of uniformity in the moisture content of the surface of individual eggs during the grading process, and the significant amount of dust created during the laser marking process, among other things, have made it challenging to mark individual eggs with sufficient accuracy, reliably and consistency for certain purposes.